The present invention relates generally to sealed bulkhead feedthrough units or assemblies for feeding optical fibers and/or electrical leads from underwater cables through a bulkhead into an equipment housing for connection to components in the housing, or for example, through the bulkhead of a submarine.
A bulkhead feedthrough assembly has a first end for coupling to an underwater cable and a second end for coupling to a port in a bulkhead, and has a through bore for feeding optical fibers and electrical leads through the assembly into the housing. However, the fibers and/or leads must be sealed in the through bore in order to prevent seawater from entering the housing should there be a cable leak or other failure outside the housing. Up to now, feedthrough bores have generally been sealed by filling the space around the fibers or leads with epoxy cement, or by using "stuffing tubes" which are high-stress packing glands. Each of these methods is subject to several disadvantages. For epoxy-filled bores, for example, once the bore is filled with epoxy, the connection is permanent and the cable can no longer be disconnected, moved, or adjusted. Secondly, the epoxy can create pressure points on optical fibers, which in turn can distort the fibers and possibly block passage of light signals through the fibers. For packing glands, the extreme forces required to compact the gland material enough to form a pressure-tight seal distorts and compresses the sometimes fragile elements (i.e. optical fibers) that pass through it, thereby creating destructive stresses.